Question

How can I implement recursive MySQL Queries. I am trying to look for it but resources are not very helpful.

Trying to implement similar logic.

public function initiateInserts()
{
    //Open Large CSV File(min 100K rows) for parsing.
    $this->fin = fopen($file,'r') or die('Cannot open file');

    //Parsing Large CSV file to get data and initiate insertion into schema.
    $query = "";
    while (($data=fgetcsv($this->fin,5000,";"))!==FALSE)
    {
        $query = $query + "INSERT INTO dt_table (id, code, connectid, connectcode) 
                 VALUES (" + $data[0] + ", " + $data[1] + ", " + $data[2] + ", " + $data[3] + ")";
    }
     $stmt = $this->prepare($query);
     // Execute the statement
     $stmt->execute();
     $this->checkForErrors($stmt);
}

@Author: Numenor

Error Message: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '0' at line 1

This Approach inspired to look for an MySQL recursive query approach.

Here is the Approach I was using Earlier:

Current Code:

public function initiateInserts()
{
    //Open Large CSV File(min 100K rows) for parsing.
    $this->fin = fopen($file,'r') or die('Cannot open file');

    //Parsing Large CSV file to get data and initiate insertion into schema.
    while (($data=fgetcsv($this->fin,5000,";"))!==FALSE)
    {
        $query = "INSERT INTO dt_table (id, code, connectid, connectcode) 
                 VALUES (:id, :code, :connectid, :connectcode)";

        $stmt = $this->prepare($query);
        // Then, for each line : bind the parameters
        $stmt->bindValue(':id', $data[0], PDO::PARAM_INT);
        $stmt->bindValue(':code', $data[1], PDO::PARAM_INT);
        $stmt->bindValue(':connectid', $data[2], PDO::PARAM_INT);
        $stmt->bindValue(':connectcode', $data[3], PDO::PARAM_INT);

        // Execute the statement
        $stmt->execute();
        $this->checkForErrors($stmt);
    }
}

Updated Code

public function initiateInserts()
{
    //Open Large CSV File(min 100K rows) for parsing.
    $this->fin = fopen($file,'r') or die('Cannot open file');

    //Prepare insertion query to insert data into schema.
    $query = "INSERT INTO dt_table (id, code, connectid, connectcode) 
                 VALUES (:id, :code, :connectid, :connectcode)";

    $stmt = $this->prepare($query);
    // Then, for each line : bind the parameters
    $stmt->bindValue(':id', $data[0], PDO::PARAM_INT);
    $stmt->bindValue(':code', $data[1], PDO::PARAM_INT);
    $stmt->bindValue(':connectid', $data[2], PDO::PARAM_INT);
    $stmt->bindValue(':connectcode', $data[3], PDO::PARAM_INT);

  //Loop through CSV file and execute inserts prepared, but this is not working
  //and there are not data being populated into database. 
   while (($data=fgetcsv($this->fin,5000,";"))!==FALSE)
        {
            // Execute the statement
             list($id, $code, $connid, $conncode)=$data;

            $stmt->execute();
            $this->checkForErrors($stmt);
        }
    }

This was my Main Question for which I am looking for suggestions !!!

Answer 1

• There’s nothing recursive in that code snippet.
• The wrong operator is used to concatenate the strings, it’s . (dot) not +
• You’d have to use something like mysqli::multi_query() to execute more than one statement with a single function call and the statements would have to be separated by a delimiter character (by default a semicolon)
• Since you’re already using prepare() and execute() why not simply make it a parametrized prepared statement and then assign the values in each iteration of the loop and execute the statement? (Exactly what is $this and what type of object does $this->prepare() return?)
• edit and btw: $this->prepare() indicates that your class extends a database class. And it also holds a file descriptor $this->fin. This has a certain code smell. My guess is that your class uses/has a database/datasink object and a file/datasource, but not is a database+readfile class. Only extend a class if your derived class is something.

edit: a simple example

class Foo {
  protected $pdo;
  public function __construct(PDO $pdo) {
    $this->pdo = $pdo;
  }

  public function initiateInserts($file)
  {
    $query = '
      INSERT INTO
        dt_table_tmp
        (id, code, connectid, connectcode)
      VALUES
        (:id, :code, :connid, :conncode)
    ';
    $stmt = $this->pdo->prepare($query);
    $stmt->bindParam(':id', $id);
    $stmt->bindParam(':code', $code);
    $stmt->bindParam(':connid', $connid);
    $stmt->bindParam(':conncode', $conncode);

    $fin = fopen($file, 'r') or die('Cannot open file');
    while ( false!==($data=fgetcsv($fin,5000,";")) ) {
      list($id, $code, $connid, $conncode)=$data;
      $stmt->execute();
    }
  }
}

$pdo = new PDO("mysql:host=localhost;dbname=test", 'localonly', 'localonly'); 
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// set up a demo table and some test data
$pdo->exec('CREATE TEMPORARY TABLE dt_table_tmp (id int, code int, connectid int, connectcode int)');
$sourcepath = 'sample.data.tmp';
$fh = fopen($sourcepath, 'wb') or die('!fopen(w)');
for($i=0; $i<10000; $i++) {
  fputcsv($fh, array($i, $i%4, $i%100, $i%3), ';');
}
fclose($fh); unset($fh);
// test script
$foo = new Foo($pdo);
$foo->initiateInserts($sourcepath);